1. Field of the Invention
This invention relates to outboard electric motors for boats, and more particularly to such outboard electric motors that are lightweight, portable and require little or no maintenance.
2. Description of the Related Art
Operators of oar driven small boats, such as dinghies, canoes, kayaks and inflatable watercraft, find it sometimes desirable to propel their boats using an electric motor. Ideally, the electric motors and their batteries should be sufficiently lightweight so they may manually carried and adaptable or attachment to different transoms or transom bars.
Typical outboard electric motors on small boats consist of direct drive motor units mounted inside a submerged housing. Such outboard electric motors use relatively small propellers that measures 5 to 11 inches in diameter. While such propellers are relatively small and inefficient at speeds under 10 mph, the higher RPM and torque requirements of large propellers make them unsuitable for direct drive electric motors. In addition, because the drive motor units are submerged, leaks around the housing is a failure point.
There are two types of gear systems used with outboard electric motors—sealed gear systems in which the gears and bearings lubricated with grease are used to rotate a propeller are all located in a watertight, sealed housing; and non-sealed gear systems in which the gears and bearings are located in a non-watertight housing in which water flows and in direct contact with the gears and bearings and acts as a lubricant.
One drawback with watertight, sealed gear systems is that the gears and bearings must periodically cleaned and re-greased. Another drawback is that the watertight, sealed system is that the watertight housing can fail allowing water or moisture to enter and damage the gears and bearings.
One drawback with non-watertight gear systems is that water has lower lubricating properties than grease making the gears and bearings vulnerable to greater wear and corrosion. As a result, the gears and bearings used in non-watertight gear systems must be replaced more often which heretofore has been more expensive and time consuming than lubricating the gears and bearings in watertight, sealed systems.
Many small boats with electric motors are operated in small bodies of water that are shallow and require the small boat to be run aground on the beach to load and unload. As a result, the motor's lower shaft and propeller often contact submerged objects or the ground. To prevent damage to the lower shaft or propeller, the mounting system used to mount the electric motor must either allow the user to selectively swing the electric motor out of the water or allow the lower shaft to freely swing upward when impacting submerged objects.
Some small boats, such as dinghies and kayaks, have built in transoms upon which an electric motor can be mounted. Some small boats, such as canoes, do not have transoms and therefore require a secondary transom plate adaptor mounted on the side of the boat upon which an electric motor can be mounted. Because the angle of the transoms or the transom plates can vary, the transom mount used with outboard electric motors must be adjustable for different transom angles.
U.S. Coast Guard regulations require that batteries used with outboard electric motors be securely attached at a fixed location inside the boat. Heretofore, secondary straps and buckles have been used to attach the batteries directly to a boat surface. Unfortunately, not all small boats have battery straps or buckles or surfaces for affixing a battery. In addition to holding the battery in a fixed location inside the boat, attaching the batteries to the boat is especially important because small boats can easily overturn in the water causing all non-buoyant objects, such as an electric batteries to be lost.